African blood has run through British veins since at least the 18th century and perhaps since Roman times, a study suggests. A set of typically West African genes has been found in seven white British men who share the same rare surname, allowing scientists to trace an African heritage that none had any idea he shared.

The African Y chromosome — the packet of genetic material passed down through the male line — probably originated from a man from Senegal or Guinea-Bissau who lived in Yorkshire in the early 18th century and was inherited by his male descendants.

It is even possible that the line goes back farther still, to Roman soldiers from North Africa posted to Hadrian’s Wall 1,800 years ago. This “division of Moors”, which included the earliest known Africans in Britain, included recruits from what is now Morocco.

Mark Jobling, professor of genetics at the University of Leicester, who led the research, said that it offered a fascinating insight into the history of black Africans in Britain. “This study shows that what it means to be British is complicated and always has been,” Professor Jobling said.

“Human migration history is clearly very complex, particularly for an island nation such as ours, and this study further debunks the idea that there are simple and distinct populations or ‘races’ . . . This chromosome has nothing to do with how you look or how you are, beyond making you male. But it is a very reliable marker of African ancestry.”

The study, which was funded by the Wellcome Trust and published in the European Journal of Human Genetics, found that one white man had a very unusual Y chromosome variant normally found in West Africa.

The man, termed “Mr X”, has a rare surname that is typical of Yorkshire. The scientists then tested 18 other men with the same surname. Six had the African Y chromosome. Registers were then used to trace each man’s genealogy, leading to two families in Yorkshire in the late 18th century. The chromosome’s West African origin suggests that their common ancestor probably reached Britain via the slave trade.